Beta adrenergic blockade with propranolol can relieve angina pectoris, and may improve survival in some patients with coronary artery disease. However, because it reduces contractility, it may cause clinically important left ventricular dysfunction in some patients with coronary artery disease, and therefore is often withheld if evidence of left ventricular dysfunction exists in the absence of drug. However, it is possible that by reducing myocardial oxygen demand in such patients, propranolol might actualy prevent ischemic dysfunction which otherwise might occur during stress. We are testing the efficacy of propranolol in this setting with the use of non-invasive radionuclide cineangiography, to determine whether the drug should be administered more freely to patients with coronary artery disease and left ventricular dysfunction.